Axial flow reversible fan

ABSTRACT

The axial-flow reversible fan disclosed consists of a sectional housing mounting impellers which produce an air flow during the operation of the fan. Disposed steamwise inside the housing is a device for straightening and guiding the air flow equipped with rotaty guide blades. The latter have a concavo-convex aerodynamical profile in the passage section and have a trapezoidal shape in the non-passage section, the major base of said trapezium being made along the radius of the fan, while the chords are equal to 2 pi R/Z, where R is the radius varying within the length of the rotary guide blade and Z is the number of these blades. The rotary guide blades through their tails are connected to the mechanism which provides for turning the blades through an angle close to 180*.

United States Patent [191 Agushev et al. 3

[ June 28, 1974 1 AXIAL-FLOW REVERSIBLE FAN [22] Filed: May 12, 1972 [21] Appl. No.: 252,745

[52] US. Cl. 415/152, 415/160 [51] Int. Cl. F01d 1/30, FOld 17/14 [58] Field of Search 415/129, 130, 147, 148,

[56] References Cited UNITED STATES PATENTS Moody 415/149 Hersey 415/147 Primary ExaminerHenry F. Raduazo Attorney, Agent, or Firml-1olman & Stern 5 7] ABSTRACT The axial-flow reversible fan disclosed consists of a sectional housing mounting impellers which produce an air flow during the operation of the fan. Disposed steamwise inside the housing is a device for straightening and guiding the air flow equipped with rotaty guide blades. The latter have a concavo-convex aerodynamical profile in the passage section and have a trapezoidal shape in the non-passage section, the major base of said trapezium being made along the radius of the fan, while the chords are equal to 2rrR/Z, where R is the radius varying within the length of the rotary guide blade and Z is the number of these blades. The rotary guide blades through their tails are connected to the mechanism which provides for turning the blades through an angle close to 180.

3 Claims, 11 Drawing Figures r/ 1 K Z1 I PATENTED m 3820.916v SHEET 3 0F 5 AXIAL-FLOW REVERSIBLE FAN BACKGROUND OF THE INVENTION The present invention relates to machines used for moving large volumes of air in straight and reverse directions in turn. More particularly, the invention relates to axial-flow reversible fans employed, for example, in subways, mines, and other underground and surface installations.

The ventilation system of a subway is usually built around a reversible operating cycle. It operates so that in summer the air is forced into the underground tunnels by station ventilation units and is removed therefrom through the wayside ventilation fans, while during the cold period of the year the system is reversed for active cooling of the ground surrounding the tunnels, in which case the cold outside air is fed into the tunnels through the wayside ventilation units and is removed through the station units. In this case the efiiciency of the fans during the cold period of the year must be equal to at least 80 percent of that during the direct flow ventilation in the summer time.

The mine ventilation units in the coal and ore-mining industry, according to the safety engineering requirements, must have an efficiency during the reversedflow ventilation equal at least to 60 percent of the rated capacity of the straight-flow ventilation.

At the present time the air exchange in such installations is effected by means of multiple-stage axial-flow reversible fans consisting of a housing accommodating impellers whose number depends on the number of stages, and a corresponding number of devices for directing and straightening the air flow. The impellers are rotated by the driving portion of the fan through a belt drive from an electric motor. As a rule, the air flow is reversed in these fans by changing the direction of rotation of the impellers and by turning the blades of the devices for straightening and directing the air flow, or by turning the blades of the impellers at an invariable position of the guide blades.

The latter is used less frequently because of the difficulties arising, for example, where it is necessary to turn the blades simultaneously by means of remote control.

The mechanism for simultaneously turning the guide blades is well known in the art and is widely used in high-capacity axial-flow fans. It consists of an external carrier ring swinging on rollers about the fan shell and hingedly connected to turning levers mounted on the external portions of the driving axles of the blades. The number of such mechanisms depends on the number of devices for straightening and guiding the air flow.

Such are two-stage axial-flow mine fans widely used in the USSR.

The fans manufactured by same design and application of the known foreign firms have a similar construction.

Also known in the art are fans in which the carrier ring is located not outside the fan but at the blade faces On employing the above system for reversing the direction of the air flow of the fan, its actual efficiency is reduced to 40-45 percent of the rated efficiency of the direct flow, and this value does not meet the requirements of ventilation of subways and mines; this therefore, is the main disadvantage of such fans.

Consequently, when such fans are used under the conditions of a reversible system of ventilation with a required efficiency of the reversed flow exceeding 45 percent of the rated efficiency of the direct How, the fans themselves are not reversed, for the ventilation units are additionally equipped with by-pass channels with gates for reversing the unit as a whole or some other additional devices are used. In this case the efficiency of the ventilation units is reduced, and the size of the ventilation chambers is increased thus increasing the capital cost and complicating the service of the ventilation system.

One of the factors impeding an increase in the reverse-duty efficiency of the reversible fan itself consists in the limitation of the angular turn of the guide blades due to imperfect construction of the above-said turning mechanism of these blades.

The kinematic diagram of the mechanisms with an external carrier ring or a face ring does not allow the blades to be turned through an angle higher than while it is expedient that the aerodynamically optimum side of the guide blades is arranged streamwise, i.e. during reversal, the guide blades are to be turned through an angle of about In order to obtain such an effect by means of the known turning mechanism, attempts have been made to use flexible (rubber) blades to be transferred beyond the dead point of the bending by means of this mechanism; thereafter, the blades under the action of the air flow through a specified angle.

However, experiments with these fans have given no positive results, substantially, due to the vibrations of the blades caused by the airflow.

Another proposal consisting in turning the outlet and inlet portions of the blades of the straightening and guiding devices through small angles to solve a similar problem (cf. USSR Authors Certificate No. 203137, cl. 27c 7/05 has also not been successful due to technical difficulties.

Another disadvantage of the known blade turning mechanism is the increased size of the fan due to the mounting of the carrier ring beyond the housing which, for instance, hinders the installation of two parallel fans in a tunnel ventilation chamber of the rated overall dimensions.

Still another significant disadvantage of the known axial-flow reversible fans (particularly when they are mounted in parallel in a common ventilation chamber as is usually the case in underground application of such fans) is the need for additional valves or gates disposed streamwise in the ventilation chamber. These valves or gates are mounted for closing the passage section of each fan to prevent air flows through idle fans (when the other fans operate) and also to prevent selfrotation of the impellers of the deenergized fans under the piston effect of moving trains.

The large cross-sectional area of the air passages and the necessity to operate of these valves or gates by remote control require an increase in the length of the ventilation chambers and this fact increases the cost of erection of the ventilation system and complicates its servicing.

Furthermore, the known constructions of shutter or radial gates used for closing or controlling the air flow of general-purpose fans including those used in the cooling systems of transport vehicles (automobiles, helicopters) are characterized by poor aerodynamical profile, reduction in fan efficiency and the inability of fan reversal to be employed. Therefore, they cannot be used in axial-flow reversible fans.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages.

The main object of the invention is to provide an axial-flow reversible fan ensuring 80 percent efficiency of the directflow operation and allowing for gating the passage section of the fan which does not decrease its efficiency both under the direct-flow and reverse-flow operating conditions.

This object is attained due to the fact that in an axial flow reversible fan the blades of the device for straightening and guiding the air flow are provided with a concavo-convex aerodynamic profile in the passage section of the blades, while in the non-passage section of the blades they have a trapezoidal shape whose major base is made along the radius of the fan, whereas the chords are equal to 2 1rR/Z, where R is the radius changing within the length of the blade and Z is the number of blades, in which case said blades, through their sails are connected to a mechanism turning the blades through an angle close to 180.

The tail of the blades of the device for straightening and guiding the air flow is preferably toothed and its end provided with a freely rotating supporting roller.

It is also expedient that in the blade turning mechanism arranged inside the device for straightening and guiding the air flow the driving rim of the toothed gear is made flexible and floating at least on three supports and in combination with the spring-loaded ring embracing and wedging the toothed tails of the moving blades.

Such a fan construction makes it possible;

to turn the blades practically through any angle (in this case, for example, by an angle of 195), while setting their profile in an aerodynamically advantageous position both under the direct-flow and reversed-flow operating conditions of the fan;

to carry out an additional adjustment of the position of the blades thereby varying the capacity and pressure of the fans used in ventilation systems with unstable operating conditions which depend on the time, place or technological process;

to eliminate the play in each moving blade of the device for straightening and guiding the air flow thus eliminating their angular vibration under the action of the air flow during operation of the fan;

to close the passage section of an inoperative fan by means of the rotary blades of the device used for straightening and guiding the air flow and, owing to this fact, to dispense with the additional arrangements (gates, brakes) with which the ventilation systems are usually equipped;

to mount the blade turning mechanism inside the device for straightening and guiding the air flow without increasing the overall dimensions of the fan.

This makes it possible to increase the technical and economical characteristics of the fan (capacity, pressure, efficiency) under direct-flow and, particularly, reversed-flow operating conditions, provides for satisfactory noise-level characteristics, maintains the basic overall dimensions and weight of the axial reversible fan at the level of the known machines of this type.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will be apparent from the following detailed description of some embodiments of the invention, reference being made to the accompanying drawings, in which:

FIG. 1 is a longitudinal section of the axial-flow reversible fan according to the invention;

FIG. 2 is a side view of the same;

FIG. 3 is a longitudinal section along the blade turning mechanism;

FIG. 4 is a view of the unit for mounting and turning the blades of the device straightening and guiding the air flow;

FIG. 5 is a sectional view of the device shown in FIG. 3 taken through the blade turning mechanism;

FIG. 6 is the same as in FIG. 1 in a sectional view through the device straightening and guiding the air flow at a closed (gated) passage section of the fan;

P167 is a longitudinal section of the unit shown in FIG. 3;

FIG. 8 is the same as in FIG. 1 in a cross section taken through the device for straightening and rectifying the air flow during the direct-flow operation of the fan;

FIG. 9 is the same as in FIG. 5 in a longitudinal section;

FIG. 10 is the same as in FIG. 1 in a cross section through the device straighteningand guidingthe air flow during the reverse-flow operation of the fan;

FIG 11 is the same as in FIG. 7 in a longitudinal section DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The axial-flow reversible fan (FIGS. 1,2) consists of a sectional housing 1 accommodating impellers 2, whose number is determined by the aerodynamic diagram of the fan, and devices 3 for straightening and guiding the air flow disposed streamwise, the number of these devices also being determined by the same aerodynamic diagram.

The torque is transmitted to the impellers 2 through an associated shaft 4 rotating in bearing units 5 resting on the housing 1. The shaft is driven by an electric motor 6 through a pulley 7, a belt drive 8 and a pulley 9 secured on the shaft 4.

The axial-flow reversible fan is equipped with inlet manifolds 10 with guarding networks 11, while the devices 3 for straightening and guiding the air flow are closed at their end faces with cups or cowls 12.

Each device 3, for straightening and guiding the air flow, comprises rotary guide blades 13 (FIGS. 3, 4, and 5) the basic purpose of which is to straighten the air flow twisted by the impellers or to direct this flow to the impeller 2. The number of the rotary guide blades 13 and their profile in a passage position depend on the aerodynarnical diagram of the axial-flow reversible fan.

To perform another function, i.e. to operate as a gate, the rotary guide blades, in addition to a concavoconvex profile in the passage section, have a trapezoidal shape in the non-passage section, the major base of the trapezium corresponding to the radius of the axialflow reversible fan, while the chords are equal to b 2 *rrR/Z, where R is the radius varying with the length of the blade and Z is the number of blades.

For example, when the diameter of the axial-flow reversible fan is equal to 2.4 m, measured from the bushing of its impellers and the devices straightening and guiding the air flow constitute 0.6 of this diameter (i.e. 1.44 m), the length of the blades is equal to 2.4 1.44/2 0.48 m. When the number of blades in each for straightening and guiding the air flow is 14 the dimensions of the chords of the trapezoidal profile of the blades will constitute a series of values varying from b 2rr2.4/2.14 0.538 m to b 21r1.44/2.14 0.323 m depending on the radius R on which the chord is calculated. The radius R, in turn, will vary with the length of the blade from R 2.4/2 1.2 m to R 1.44/2 0.72 m.

Such a shape of the rotary guide blades 13 enables the passage section of the axial-flow reversible fan to be practically closed.

Each rotary guide blade 13 (FIG. 4) carries a radial tail 14 which pass through the bushing 15 of the device 3 straightening and guiding the air flow, and is secured therein so as to be rotatable and its end portion is provided with a gear 16 and a freely rotating roller 17. In addition, one of the rotary guide blades 13 also carries an external tail 18 (FIG. 3) projecting from the housing 1 of the axial-flow reversible fan through a suitable opening.

The rotary guide blades 13 (FIGS. 4 andS) are rotated and adjusted to a required angle with respect to the air flow passing inside each device 3 straightening and guiding this flow by means of a turning mechanism consisting of a gear drive, for example a bevel drive, in which the gears 16 mounted of the tails 14 of the rotary guide blades 13 are turned through an equal angle by a toothed rim 20 floating on three supports 19. The toothed rim 20 is operated by a servomotor 21 (FIG. 3) through one of the tails 18 of the rotary guide blades 13 disposed outside the axial flow reversible fan.

The construction of the toothed rim 20 (FIGS. 4 and 5) can be simplified by making it in the form of separate sectors mounted on a carrier disk 22.

The toothed rim 20 together with the ring 23 embrace the internal tails 14 and wedges the gears 16 mounted thereon, thus eliminating the play of the rotary guide blades 13. The force of wedging the gear drive is controlled by tensioning the springs 24 (FIG. 4) of suspension of the ring 23, while its reaction is taken by the rollers 17.

The centring of the toothed rim 20 with its carrier disk 22 with respect to the fan axis is effected by adjusting the supports 19 which, for example, are in the form of rollers.

Depending on the conditions of mounting of the axial-flow reversible fan, the servomotor 21 (FIG. 3) can practically be arranged on any of the rotary guide blades 13 of the device 3 straightening and guiding the air flow (shown in FIG. 2 by a dotted line).

The axial-flow reversible fan is supplied with local or remote control desks, equipped with safety and monitoring devices, for example, for checking the position of the rotary guide blades 13, the condition of the bearing units 5, and is provided with a lubrication system (not shown).

The axial-flow reversible fan is mounted in a ventilation chamber on a foundation and is secured thereto; the electric motors of the drive of the blade turning mechanism are connected to the power mains.

The axial-flow reversible fan operates as follows.

When the fan is switched on for direct-flow operation, first, each servomotor 21 (FIG. 3) is energized which through the external tail of one of the rotary guide blade 13 rotates the toothed rim 20 and through the latter transfers the rotary guide blades 13 (FIG. 7) of the device 3 straightening and guiding the air flow from the closed position to the working position by setting the rotary blades 13 (FIGS. 8,9) in a position necessary for the direct-flow operation of the fan; thereafter the electric motor 6 through the pulleys 7 and 9 and the belt drive 8 rotates the shaft 4 in the bearing units 5 and accelerates the impellers 2 mounted on this shaft to the rated speed.

The rotation of the impellers 2 (FIG. 1) creates an air flow straightened and guided by the rotary guide blades 13 (FIG. 3). The velocity and pressure of this flow depend on the rotational speed of the impellers 2 (FIG. 1), are specified by the aerodynamical calculations and are controlled by the speed ratio of the pulleys 7 and 9 of the belt drive 8.

Under the action of the springs 24 (FIG. 4) the teeth of the flexible toothed rim 20 wedge the gear 16 thus eliminating the possible angular vibration of the blades 13 under the action of the air flow.

Fan reversal is effected by changing the direction of rotation of its impellers 2(FIG- 1) after they have come to rest due to reversing the direction of rotation of the electric'motor 6 and turning the blades 13 (FIG. 3) of the device 3 (FIG. 1) 1) for straightening and guiding the air flow, by setting the blade turning mechanisms to the reverse position as described above. To this end, the blades 13 (FIGS. 10, 11) are set in the optimum position, with respect to the reversed air flow, by turning them through a common angle close to (in our case by The play of the blades 13 is then eliminated as described above.

When the fan is rendered non-operative, the driving motor 6 of the impellers 2 (FIG. 1) is switched off, and the servomotor 21, through the blade turning mechanism, sets the blades 13 (FIG. 3) to the closed or gated position, in which the blades 13 due to their trapezoidal shape completely close the passage section of the fan.

The control system of the fan is equipped with interlocking devices so that the fan can be started only in the above-described order, namely, the servomotor 21 is first switched on and through its blade turning mechanism, transfers the blades 13 from the closed (gated) position to one of the working positions, direct-flow or reverse-flow, depending on a required direction of the air flow; then the electric motor 6 (FIG. 1) is energized which drives the impellers 2.

The fan is stopped in a reverse order, namely: first, the electric motor 6 driving the impellers 2 is switched off, and then the servomotor 21 is deenergized and through its blade turning mechanism resets the rotary guide blades 13 (FIG. 3) to the closed (gated) position from any working position.

Let us consider the main characteristics of the proposed axial-flow reversible fan.

Reverse-flow efficiency (maximum),

The construction of the axial-flow reversible fan makes it possible to run it at a rotational speed of the impellers of up to 500 rpm.

In this case the capacity of the axial-flow reversible fan operating under the direct-flow conditions rises up to 310,000 m /hour, while the total pressure created by the fan is equal to 190 kg sec/m These characteristics correspondingly increase during the reverse-flow operation as well.

We claim:

1. An axial-flow reversible fan comprising in combination: a housing; impellers mounted in said housing and producing an air flow during their rotation; means for straightening and guiding said air flow, said means mounted streamwise in said housing and having rotary guide blades supplied with tails; said rotary guide blades of said means for straightening and guiding said air flow having a concave-convex aerodynamical profile in the passage section of the blades and a trapezoidal form in the non-passage section of the blades, said trapezoidal form having its major base along the radius of said fan, with the chords of said trapezoidal form being equal to 2 'n'R/Z, where R is the radius varying with the length of said rotary guide blades and Z is the number of said blades; a blade turning means connected to said blades through said tails, said turning means ensuring rotation of said blades through an angle close to whereby a high reverse efiiciency is insured and whereby the passage section of the fan is gated without a decrease in efficiency under both direct flow and reverse flow operating conditions.

2. An axial-flow reversible fan as claimed in claim 1, in which said tails of said rotary guide blades of said means for straightening and guiding the air flow are toothed, and a freely rotating supporting roller is mounted at the end of each said tail.

3. An axial-flow reversible fan as claimed in claim 1, wherein said blade turning mechanism positioned inside said means for straightening and guiding the air flow is provided with a gear drive, said gear drive having a flexible driving toothed rim and associated spring ring floating on at least three supports, said rim together with said ring associated therewith embracing and wedging the tails of said rotary guide blades. 

1. An axial-flow reversible fan comprising in combination: a housing; impellers mounted in said housing and producing an air flow during their rotation; means for straightening and guiding said air flow, said means mounted streamwise in said housing and having rotary guide blades supplied with tails; said rotary guide blades of said means for straightening and guiding said air flow having a concave-convex aerodynamical profile in the passage section of the blades and a trapezoidal form in the non-passage section of the blades, said trapezoidal form having its major base along the radius of said fan, with the chords of said trapezoidal form being equal to 2 pi R/Z, where R is the radius varying with the length of said rotary guide blades and Z is the number of said blades; a blade turning means connected to said blades through said tails, said turning means ensuring rotation of said blades through an angle close to 180* whereby a high reverse efficiency is inSured and whereby the passage section of the fan is gated without a decrease in efficiency under both direct flow and reverse flow operating conditions.
 2. An axial-flow reversible fan as claimed in claim 1, in which said tails of said rotary guide blades of said means for straightening and guiding the air flow are toothed, and a freely rotating supporting roller is mounted at the end of each said tail.
 3. An axial-flow reversible fan as claimed in claim 1, wherein said blade turning mechanism positioned inside said means for straightening and guiding the air flow is provided with a gear drive, said gear drive having a flexible driving toothed rim and associated spring ring floating on at least three supports, said rim together with said ring associated therewith embracing and wedging the tails of said rotary guide blades. 